Could nuts be one of the secret ingredients to weight loss? A couple of studies have found a correlation between relatively high nut consumption (two or more servings a week) and avoidance of weight gain and obesity. Researchers at Harvard-affiliated Beth Israel Deaconess Medical Center reported results in 2010 from a small (20 volunteers) study that showed walnuts at breakfast gave people a pre-lunch feeling of fullness that might make it easier to eat less. Ultimately, weight loss is about reining in calorie consumption (and increasing physical activity). But if nuts make people feel full, perhaps they can help lower calorie counts over all, even as they add to those totals.

Nuts are dense little packages of fat and protein, with most of the fat being the healthful, unsaturated kind. They don't contribute much in the way of vitamins but make up for it by supplying respectable amounts of potassium, magnesium, and several other required minerals.

Dieters have tended to stay away from nuts because the fat content makes them a high-calorie food. It doesn't help that we tend to shovel them in as snacks, not as part of meals. But nuts contain very little carbohydrate, so they're showing up in low-carb diets these days, particularly the ones that emphasize plant-based foods.

Nutrients in nuts per 1.5 ounces (43 grams)
	Calories	Fat (grams)	Protein (grams)
Almonds	254	22.5	9.4
Brazil nuts	279	28.2	6.1
Cashews	244	19.7	6.5
Hazelnuts	275	26.5	6.4
Macadamias	305	32.4	3.3
Peanuts	249	21.1	10.1
Pecans	302	31.6	4.0
Pistachios	243	19.6	9.1
Walnuts	278	27.7	6.5
Source: Report of the Dietary Guidelines Advisory Committee, 2010.

Nuts and your heart

Apart from weight issues, nuts seem to have some protective effects against heart disease. Numerous studies have shown that if you put people on nut-filled diets, favorable effects on cholesterol levels, blood pressure readings, and inflammatory factors follow. And in large epidemiologic studies, high nut consumption has been associated with lower rates of heart disease. An analysis of data from the Harvard-based Nurses' Health Study showed that having one serving of nuts a day is associated with a 30% lower risk of heart disease compared with having one serving of red meat a day.

A plate full of walnuts for dinner tonight?

Nuts as a meal may not sound very appealing. But cookbooks are full of recipes that incorporate nuts into pasta dishes and the like. And it would be easy for most of us to add almonds or walnuts to a bowl of cereal or low-fat yogurt at breakfast and occasionally eat a meatless lunch or dinner.

Nuts may help with diabetes, too. The lack of carbohydrate content means nuts don't add appreciably to the surges in blood sugar we experience after many meals. In fact, they can blunt the effects of carbohydrates on blood sugar levels. Those "postprandial" spikes in blood sugar contribute to the development of diabetes in people vulnerable to getting the disease and must be controlled in those who have already have it. Yet the evidence for nut consumption reducing the risk for developing diabetes is mixed, as are results of studies of the effect it has on blood sugar levels.

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Floaters

Q. I'm 55 years old, and I only need glasses for reading. Recently though, I've seen tiny black specks that move around in random directions. My eyes are not red, watery, or painful, but I'm worried that I may have the start of an eye disease.

A. The short answer is that your symptoms suggest a common and medically unimportant problem called floaters. But since your eyesight could suffer if you neglect flashes or the sudden appearance of large or numerous floaters, a long answer may be helpful.

The large chamber at the back of your eye is filled with a protein-rich, jelly-like material called the vitreous. In youth, the vitreous is completely clear and transparent, allowing light to pass freely to the back of the eyeball, where the retina collects photic energy and turns it into nerve impulses that the brain reconstructs into images.

Like all parts of the body, the eye changes with age — that's why you've come to need reading glasses. As the vitreous ages, it accumulates debris composed of tiny clumps of cells, slender threads of protein, or little knots of the vitreous gel itself. The debris literally floats through the otherwise clear vitreous, temporarily blocking a small portion of light from reaching the retina. In effect, the debris casts small shadows on the retina, which you see as small dots or threads moving through your field of vision.

Innocent floaters often drift out of the line of sight, so most people notice them intermittently. They tend to be most prominent — and annoying — when you're looking at a bright white background. There is no way to rid your eye of floaters, but you may be able to lessen the nuisance by looking up and down or from side to side.

But you should know that the aging vitreous can sometimes cause real mischief. That's because as the vitreous ages, it shrinks. As this happens, it may pull on the retina, thus activating photoreceptor cells and producing brief flashes of light. The shrinking vitreous can also tug hard enough to cause a small amount of bleeding in the retina, releasing blood cells that become new floaters.

Brief flashes and small floaters are little more than annoying reminders that we're not young anymore. But more impressive flashes or showers of new floaters can indicate that the vitreous has pulled hard enough to tear the retina or detach a portion of this critical tissue from its perch at the back of the eye. In addition to producing flashing lights and large floaters, retinal detachments may also appear as if a curtain is being drawn across the field of vision in one eye or, most seriously of all, as a sudden loss of detailed, sharp central vision in one eye.

Retinal tears and detachments can be repaired, most often by laser photocoagulation or cryopexy (freezing), but these "spot welding" techniques must be performed promptly, often within 24 to 48 hours of diagnosis. That qualifies a retinal detachment as a true medical emergency.

There's no reason to become preoccupied with your typical, innocent floaters, but you should keep alert for more worrisome visual symptoms. And even if you don't have warning symptoms, you should get a thorough eye exam and regular eye care.

— Harvey B. Simon, M.D.
Editor, Harvard Men's Health Watch